Selenium rectifier



Nov. 4, 1941. QQPPE 2,261,725

SELENIUM RECTIFIER Filed June 13, 1939 WITNESSES: INVENTOR I a Georg flap 0e.

Patented Nov. 4; 1941 2,261,725 I snmmumnac'rrma Georg Hoppe, Berlin, Germany, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 13, 1939, Serial No. 278,841

In Germany May 18, 1938 3 Claims, (01. 175-366) My invention relates to contact rectiflers and particularly to selenium rectiflers.

An element for a selenium rectifier of high power is, in accordance with the invention, produced by bending out of a large sheet disk, the surface which is to be provided with the rectifying selenium layer. A rectifier element constructed in this manner is illustrated in the drawing. The details of the method of production will be explained with reference to the drawing. Figure 1 shows the element, Fig. 2 the cross section of a rectifier element construction in accordance with the invention as exemplary embodiment,

The metal part 2 is pressed out of a round disk I, thereby the possibility is availed of depositing the layer of fused selenium on this projecting portion 2 without the loss of considerable amounts of the valuable selenium material. The remaining portion of the disk I projects over the metal portion 2, serves in the operation for' conducting away heat and, therefore, makes possible the loading of the rectifying layer with an essentially larger current density than is possible without the current conducting wide rim.

It is desirable to construct the disk I of aluminum since the latter is cheap and has only a small weight. In addition it is a good'heat-conduct'or so that the heat transfer is very effective,

The formation of the rectifier may, in such a case, for example, take place in the following manner; the bent out center surface 2 is freed of its usual oxide layer with the aid of a sand blast and, at the same time, roughened. On this now clean metal surface, the liquid selenium is deposited. At the same time, because of the bending out, it is possible to avoid the deposit of L,

substantially large amounts of selenium on the rim of the disk which should serve only for conducting heat away. The central portion cover with the selenium layer 3 is subjected, under a press, to a sufficient pressure which makes possulphur layer produced in this manner, a low A melting temperature metal is sprayed, for example, an alloy of lead or bismuth, or cadmium or bismuth. Care must be taken that the sprayed on layer is sufflciently pure.'

A direct current potential in the blocking direce tion is-then impressed on the'rectifier disks prepared ln this manner. It may amount, for example, to 8-10 volts, suflicient current passing in the blocking direction to cause the disk to become quickly heated. In, doing this, the electrical resistance increases and this can be'recognized by an increase in the potential. As soon as the potential has arisen to approximately 18 volts, the formation of the rectifier element is finished. In the blocking direction, there passes, at this potential, only current of a few milliamperes.

After this the necessary number of rectifier disks are, in the usual manner, disposed over each other and the rectifier thus produced may, as a consequence of the good heat transfer by the rim surrounding it in a ring, be loaded substantially higher than is otherwise the case. The disk I may also be composed of copper or one of its alloys, and when such good heat conduction is not required, also of a metal of the iron group. i The disk may also'first be provided with a suitable base for the selenium layer consisting of another metal or of graphite for the purpose of dewhich is bent out so that it lies in a different plane than the remaining surface and a deposit of selenium on said bent out surface, said remaining surface surrounding said deposit.

3. A selenium rectifier comprising an integral plate of aluminum alloy, a portion of the surface of which is bent out so'that it lies in a different plane than the remaining surface and a deposit of selenium on said bent out surface, said remaining surface surrounding said deposit.

GEORG HOPPE. 

